Electronic watch equipped with solar cell

ABSTRACT

An electronic watch is formed of a case body having a display window, a movement situated in the case body, a light transmitting digital display disposed above the movement in the case body to be observed from an outside through the display window, and a solar cell unit. The solar cell unit is interposed between a part of the light transmitting digital display and the movement, and a reflecting plate is disposed under another part of the light transmitting digital display adjacent to the solar cell unit. Also, a light transmitting material is interposed between the part of the light transmitting digital display and the solar cell unit. Thus, light is supplied to the solar cell unit from the outside through the light transmitting digital display.

FIELD OF THE INVENTION

This invention relates to an electronic watch equipped with solar cell,and, especially, to an electronic watch equipped with a solar cellprovided with a digital display which has a large area for supplyinglight to a solar cell unit to generate sufficient power and allows thedigital display to occupy a large area and to be easily seen, therebyrealizing an ecological watch having a high product value.

DESCRIPTION OF THE BACKGROUND ART

In recent years, electronic watches provided with a solar cell unit havebeen proposed, in which electric power generated by the solar cell unitis charged to a condenser or a secondary battery and the generated poweris utilized to drive these watches.

Such an electronic watch uses a solar cell unit as a power source sothat no replacement of a cell is required. This technology has met arecent enhanced ecological demand and is hence rapidly becomingwidespread throughout various fields.

Here, In the case of mounting a solar cell unit in an extremely smalldevice such as a watch, it is necessary to supply with certaintysufficient light to a solar cell. Because of this, it is desirable thatthe solar cell unit be disposed at a dial portion possessing the largestarea in the watch.

While, in simple analog type watches which display the time using threeor two hands, the design of a dial is of the most importance. It istherefore undesirable for the design of the watch with a solar cellhaving a deep violet color, if such solar cell appears on a dialportion.

For the above reason, in conventional analog type watches, a solar cellunit is disposed on the dial and a light transmittable material with awhite or another color is arranged on the solar cell to avoid directexposure of the solar cell and thereby to improve the design of thewatch while sufficient light is supplied to the solar cell.

At present, extremely simple and usual watches such as theaforementioned analog type watches which display the time using three ortwo hands are widely received in the market. On the other hand, unusualwatches such as watches adopting a digital display using a liquidcrystal cell or the like to display the time are also favorablyreceived.

Such a digital display watch, however, has various structural problemswhen using a solar cell unit as a power source.

The analog type watch has no problem with its functions if a solar cellunit is disposed on the dial. Also, the design problem can be solved byarranging the light transmittable material with various colors on thesolar cell.

However, in the digital display watches, when a solar cell unit ismounted on a digital display, the solar cell covers the digital displayand hence the display is not viewed. It is therefore impossible todispose a solar cell unit over the entire display in the same manner asin the analog watches.

If a solar cell unit is disposed below the digital display, there is theproblem that light is not supplied to the solar cell. More concretely, aliquid crystal display material constituting a digital display isgenerally provided with a reflecting plate at the lowest side thereof toeasily distinguish characters and the like displayed by a liquid crystalcell. If the solar cell unit is disposed below such a digital display inthe above manner, incident light from the outside is reflected by thereflecting plate so that no light is supplied to the solar cell. It istherefore impossible to dispose the solar cell unit below the liquiddisplay material in the conventional digital display electronic watches.

As a structure provided with a solar cell unit in the digital displaywatch, to date there has only been a structure such as disclosed, forexample, in Japanese Patent Application Laid-open No. 287427/1990 inwhich a solar cell unit is disposed on a digital display at a positionwhich never overlaps a liquid crystal cell. Such an arrangement isgeneral at present.

However, in the structure in which the solar cell unit is disposed insuch a manner as disclosed in Japanese Patent Application Laid-open No.287427/1990, almost all parts of the watch surface on which the digitaldisplay is arranged are covered with the solar cell. Hence, the area forthe digital display for displaying the essential time and the like isconsiderably narrowed, presenting a fatal problem for a watch inasmuchas the time and the like can be seen only with difficulty.

As outlined above, a structure for mounting a solar cell unit hasimportant and serious problems in the case where it is intended to usethe solar cell unit in digital display watches provided with a digitaldisplay composed of a liquid crystal and the like.

Incidentally, in recent years watches such as a wrist watch have beendeveloped in which a light transmitting liquid crystal cell is used fora display to indicate the time, thereby providing a watch with aninteresting effect.

Though such a watch itself has an interesting effect, it can never be asolar cell product which can meet an ecological demand since it uses anormal battery as a power source. Also, no technology in which a solarcell is mounted in such a watch provided with a light transmittingliquid crystal cell and is allowed to function efficiently as a watchmaterial has as yet been proposed or realized.

Accordingly, the present invention has been achieved in view of thissituation and has an object of providing a electronic watch equippedwith a solar cell provided with a digital display which has a large areafor supplying light to a solar cell to generate sufficient power andwhich allows the digital display to occupy a large area and to be easilyseen, ensuring that the digital display has a large enough area toindicate multifunctional display portions, while at the same time it isan ecological watch in which a solar cell unit is mounted and charactersand the like can be easily seen, bringing about a high product value.

DISCLOSURE OF THE INVENTION

The above objects can be attained in the present invention by theprovision of an electronic watch comprising a case body provided with adisplay window; a movement situated in the case body; and a displaywhich is disposed above the movement in the case body and can beobserved from the outside through the display window, wherein thedisplay is constituted of a light transmitting digital display means, asolar cell unit is interposed between the light transmitting digitaldisplay means and the movement, and light is supplied to the solar cellunit from the outside through the light transmitting digital displaymeans.

The present invention is featured in that even if the solar cell unit isdisposed below the digital display means, sufficient light can betransmitted and supplied to the solar cell unit via the lighttransmitting digital display means and at the same time the digitaldisplay means is allowed to occupy a large display area without anyrestriction from the solar cell unit.

In preferred embodiments of the present invention, a light transmittablematerial composed of a translucent material such as a ceramic or thelike is disposed between the light transmitting digital display meansand the solar cell unit.

In this embodiment, the light transmittable material allows incidentlight from the outside to be transmitted and to be supplied to a cell ofthe solar cell unit and reflects a part of the incident light to act asa reflecting plate for the digital display whereby displays such ascharacters and the like on the digital display can be seen more easily.

Apparently, though the present invention relates to an electronic watchprovided with a digital display, it can provide a large area forsupplying light to the solar cell to allow the solar cell to generatesufficient power and allows the digital display to occupy a large areaand to be easily seen.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional front view of a main portion showing a firstembodiment of an electronic watch equipped with a solar cell accordingto the present invention.

FIG. 2 is a sectional front view showing a main portion in the vicinityof a solar cell of the electronic watch equipped with a solar cell shownin FIG. 1.

FIG. 3 is a plan view showing the finished condition of the electronicwatch equipped with a solar cell shown in FIG. 1.

FIG. 4 is a sectional front view of a main portion in the vicinity of asolar cell showing a second embodiment of an electronic watch equippedwith a solar cell according to the present invention.

FIG. 5 is a sectional front view of a main portion showing a thirdembodiment of an electronic watch equipped with a solar cell accordingto the present invention.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS

The present invention will now be explained in detail with reference tothe appended drawings.

First Embodiment

First, a first embodiment of the present invention is explained withreference to FIGS. 1, 2, and 3.

FIG. 1 is a sectional front view of a main portion showing a firstembodiment of an electronic watch equipped with a solar cell accordingto the present invention, FIG. 2 is a sectional front view showing amain portion in the vicinity of a solar cell of the electronic watchshown in FIG. 1, and FIG. 3 is a plan view showing the finishedcondition of the electronic watch shown in FIG. 1.

As shown in these figures, an electronic watch of the present embodimentcomprises a case body 1 provided with a display window 1 a; a movement 4situated in the case body 1; a display 5 which is disposed above themovement 4 in the case body 1 and can be observed from the outside viathe display window 1 a.

More concretely, the case body 1 of the watch is provided with thedisplay window 1 a in which a glass 2 is fitted and with a case back 3at the side opposite to the glass 2.

Further, a push button 9 for adjusting the time and the like is disposedat the side of the case body 1.

A movement 4 for driving the watch is disposed at the side of the caseback 3 inside the case body 1 of the watch. A display 5 for digitallydisplaying the time is disposed at the position facing the glass 2. Thisstructure allows the display 5 to be observed from above the watch viathe glass 2 and display window 1 a.

In the present embodiment, the display 5 is constituted of a lighttransmitting digital display means, specifically, a light transmittingelectro-optical display device.

This light transmitting electro-optical display device constituting thedisplay 5 in the present invention has a structure in which onlypolarizing plates are disposed on the surface and back face of a cell,excluding a reflecting plate. However, a structure may be adopted inwhich a reflecting plate and a polarizing plate are united wherein onlya part to which a voltage is applied is allowed to reflect light therebyallowing characters to appear, and the remainder is allowed to transmitlight downward.

With this structure, incident light from the outside is transmittedthrough the display 5 constituted of the light transmittingelectro-optical display device via the glass 2 and the display window 1a and is supplied to the inside of the case body 1.

Here, as shown in FIG. 1, the display 5 is formed in one larger sizethan the open area of the display window 1 a and is formed to cover theentire display window 1 a. Accordingly, the display 5 transmits allincident light entering into the display window 1 a. Also, the display5, which is formed in one larger size than the open area of the displaywindow 1 a, functions as a parting material for shielding anelectroconductive rubber 7 described below.

In the present embodiment, a solar cell unit 6 is disposed below thelight transmitting display 5, specifically between the display 5 and themovement 4, whereby the light which is transmitted through the display 5is supplied to the cell of the solar cell unit 6 since the display 5 isa light transmitting type.

Furthermore, the solar cell unit 6 to which light is supplied generatespower to drive the mechanism of the watch.

Incidentally, in place of a primary battery, a condenser or a secondarybattery which requires no replacement is incorporated into the movement4 on which the solar cell unit 6 is mounted. The power generated by thesolar cell 6 is charged to the condenser or the secondary battery todrive the watch.

A circuit substrate (not shown) is disposed at the display side of themovement 4 and is electrically connected to the solar cell unit 6. Thecircuit substrate is also electrically connected to the display 5constituted of the aforementioned light transmitting electro-opticaldisplay device by using the electroconductive rubber 7.

In addition, in the electronic watch of the present embodiment which isformed in this manner, a light transmitting material 8 is disposedbetween the light transmitting display 5 and the solar cell unit 6.

Generally, recent materials used for the solar cell unit 6 are amorphousso that a cell exhibits a deep violet color. Therefore, if the solarcell unit 6 is disposed below the light transmitting display 5,characters formed on the display 5 can be read only with difficultysince these have a color of the same type.

For this reason, in the present embodiment, the transmitting material 8formed of a translucent material such as a ceramic or the like isdisposed between the solar cell unit 6 and the display 5.

Here, the light transmitting material 8 is formed of a white translucentmaterial composed of a ceramic in the present invention.

Since the light transmitting material 8 is formed of a translucentmaterial, the light transmitting material 8 transmits a part of thelight passing through the display 5 and reflects a part of the remainderto function as a reflecting plate.

Specifically, such a translucent material of which the lighttransmitting material 8 is formed generally transmits and reflectsrespectively about 50% of the incident light. The light transmittingmaterial 8 formed of the translucent material is therefore allowed tofunction as a reflecting plate for the display 5. As outlined above, thepresent embodiment is featured in that a part of the incident lightintroduced into the watch is transmitted to the solar cell unit 6 and apart of the remainder is reflected to the side of the display 5.

Furthermore, in the present embodiment, the light transmitting material8 is disposed so as to extend under the entire display 5 whereby lightis not only transmitted to the solar cell unit 6 through all the lighttransmitting material 8 but also reflected to the display 5.

The translucent material constituting of the light transmitting material8 is not limited to ceramics or the like to the extent that it is aso-called semi-transmitting material capable of transmitting light.Other than ceramics, materials in which a large number of through-holesare formed may be used. Also, any material may be used which can supplylight to the solar cell unit 6 and can reflect light so that thecharacters such as time characters and the like formed on the display 5can be read.

Here, the structure in the vicinity of the solar cell of the electronicwatch formed in this manner in the present embodiment is now explainedin more detail with reference to FIG. 2.

FIG. 2 is a sectional front view showing a main portion in the vicinityof a solar cell of the electronic watch equipped with the solar cellshown in FIG. 1.

As shown in FIG. 2, in the present embodiment, the transmitting display5, the solar cell unit 6, and the light transmittable material 8composed of a translucent material are combined as one body by moldingtogether with a plastic material 10.

Also, as shown in FIG. 2, the plastic material 10 is provided with anopening in the front of the display 5. The plastic material 10 is alsoprovided with a through-hole 11 for inserting the electroconductiverubber 7 and a through-hole 16 for removing an electrode of the solarcell unit 6.

The display 5, the solar cell unit 6, and the light transmittingmaterial 8 are integrated with the plastic material 10 in this manner,whereby the display 5, the solar cell unit 6, and the light transmittingmaterial 8 can be handled as one block and hence the handling capabilitysuch as carriage and the like and easy assembling of a watch can beimproved. However, the plastic material 10 may be omitted as requiredand the display 5, the solar cell unit 6, and the light transmittingmaterial 8 which are separate units may be assembled to form a watch.

FIG. 3 is a plan view showing the finished condition of the electronicwatch shown in FIG. 1.

As previously mentioned, since a white translucent material formed of aceramic is used for the light transmitting material 8, the display 5consisting of the transmitting electro-optical display device displays,for example, 12:38:26 (o'clock) as a time function and 6 Month, 10 days,Mo (specifically, Monday) as a calendar function which is one offunctions other than the time function, by supplying the electric powergenerated by the solar cell unit 6.

In the present embodiment, since the display 5 consisting of thetransmitting electro-optical display device is extended over the entireelectronic watch, a wide display surface can be obtained. Also, sincethe light transmitting material 8 which is formed of a translucentmaterial such as a ceramic or the like is disposed below thetransmitting display 5, reading of characters for the time and thecalendar is quite easy.

Incidentally, the color of the transmitting material 8 which is thebackground color for the transmitting display 5 is not limited to theabove white color, and therefore various colors or patterns may be used.Specifically, it may be a color or a pattern which has a beautifulvisual appearance.

In the electronic watch equipped with the solar cell of the presentembodiment, as previously mentioned, even if the solar cell unit 6 isarranged below the display 5 consisting of a digital display means,sufficient light can be transmitted and supplied to the solar cell unit6 via the light transmitting display 5. At the same time, a largedisplay area for the display 5 is available without any restriction fromthe solar cell unit 6.

Furthermore, since the light transmitting material 8 formed of atranslucent material such as a ceramic or the like is arranged betweenthe display 5 and the solar cell unit 6, the light transmitting material8 serves to transmit and supply external light to the cell of the solarcell unit 6 and, at the same time, to reflect a part of the externallight toward the side of the display 5, thereby making it possible toeasily read a digital display such as characters and the like formed onthe display 5.

Second Embodiment

Next, a second embodiment of the present invention is now explained withreference to FIG. 4.

FIG. 4 is a sectional front view of a main portion in the vicinity of asolar cell showing a second embodiment of an electronic watch equippedwith a solar cell according to the present invention.

As shown in FIG. 4, the electronic watch equipped with the solar cell ofthe present embodiment is a modification of the aforementioned firstembodiment. In the present embodiment, a digital display 12 comprises anelectro-optical display device in which a part thereof is a lighttransmitting electro-optical display device and the remainder is a lightreflecting electro-optical display device.

Specifically, in the present embodiment, a light transmitting material13 formed of a translucent material and a solar cell unit 14 aredisposed below the display 12 so as to extend over one half of thedisplay 12 and a reflecting plate 15 is disposed below the display 12 soas to extend over the remaining half.

In the electronic watch of the present embodiment possessing such astructure, the display 12 of the side at which the reflecting plate 15is placed exhibits a display having a remarkably high contrast. At thesame time, charging can be performed at the side at which the solar cellunit 14 is placed while the time is displayed. Accordingly, it isdesirable that displays such as time and the like which are commonly andfrequently observed be disposed at the side of the reflecting plate 15and that displays such as the day and week which are intended forrelatively infrequent viewing be disposed at the side of the solar cellunit 14. Such an arrangement, in which the reflecting plate 15 and thesolar cell unit 14 are placed below the display 12 so that both extendover each half of the display 12, gives an interesting effect to thewatch.

In the present embodiment, though the light transmitting material 13(and the solar cell unit 14) and the reflecting plate 15 are placedbelow the display 12 so that both extend over each half of the display12, the ratio of each of the areas occupied by both is not limited tohalf. A structure may be adopted in which the light transmittingmaterial 13 and the reflecting plate 15 are disposed below the display12 so that both extend over at least a part of the display 12.

Third Embodiment

Next, a third embodiment of the present invention is explained withreference to FIG. 5.

FIG. 5 is a sectional front view showing a main portion of a thirdembodiment of an electronic watch equipped with a solar cell accordingto the present invention.

As shown in FIG. 5, the electronic watch equipped with the solar cell ofthe present embodiment is a modification of the first embodiment. It isprovided with an analog display means in the digital type electronicwatch shown in FIG. 1. Specifically, it is a combination watchpossessing both an analog display and a digital display.

More concretely, in the electronic watch of the present embodiment, alight transmitting material 18 formed of a translucent material and asolar cell unit 17 are disposed below a display 5 comprising a lighttransmitting electro-optical display device so that both are mounted ona movement 19 in the same manner as in the first embodiment. Also, aspace for placing an analog display means mentioned below is formedbelow the display 5.

The movement 19 drives the light transmitting electro-optical displaydevice constituting the display 5 and hands for an analog display meansmentioned below. A hand shaft 20 is formed projecting from almost thecenter of the surface of the movement 19 to a space below the display 5.

In addition, through-holes 17 a and 18 a for the hand shaft 20 areformed in the solar cell unit 17 and the light transmitting material 18respectively.

A second hand 21, a minute hand 22, and an hour hand 23 are attached tothe hand shaft 20 rotating in a space below the display 5.

Specifically, each of the hands 21, 22, and 23 is positioned between thedisplay 5 and the light transmitting material 18 and the solar cell unit17 is positioned below the light transmitting material 18.

A circuit substrate, though not shown, is disposed on the upper surfaceof the movement 19 and is electrically connected to the aforementionedlight transmitting electro-optical display device constituting thedisplay 5 through an electroconductive rubber 24. Though notspecifically shown, similarly, the circuit substrate is electricallyconnected with the solar cell unit 17. Also, a parting plate 25 isdisposed on the inside of the electroconductive rubber 24.

In the electronic watch of the present embodiment possessing such astructure in which a hand type analog display means is further providedin addition to the display 5 constituted of a light transmitting digitaldisplay means, since usual displays for the time and the like can beachieved by the analog display means, for example, the display 5constituted of a digital display means is formed of a perfectlytransmitting type. It is also possible to provide other functions ordisplays such as a chronograph, timer, and time displays for the alarmusing the digital display means while the time is displayed by theanalog display means.

Furthermore, the provision of the analog display means in addition tothe digital display means ensures that the electronic watch of thepresent embodiment is improved in quality compared with a watch havingonly a digital display.

INDUSTRIAL APPLICABILITY OF THE INVENTION

As is clear from the above illustrations, a feature of the presentinvention is that the display of an electro-optical display device canbe enlarged so that watches exhibiting easily visible characters can beobtained. Also, an area allowing other functions besides time to bedisplayed can be secured and, in addition, a solar cell with sufficientgenerating capacity is disposed in even such a small device as a watch,thereby providing an ecological watch having a high product value.Therefore, the electronic watch of the present invention is particularlysuitable for digital display watches and for combination watchesprovided with a digital display means and an analog display means.

What is claimed is:
 1. An electronic watch comprising: a case bodyhaving a display window, a movement situated in the case body, lighttransmitting digital display means disposed above the movement in thecase body to be observed from an outside through the display window, asolar cell unit interposed between a part of the light transmittingdigital display means and the movement, a light transmitting materialinterposed between said part of the light transmitting digital displaymeans and the solar cell unit so that light is supplied to the solarcell unit from the outside through the light transmitting digitaldisplay means and the light transmitting material, and a reflectingplate disposed under another part of the light transmitting digitaldisplay means adjacent to the solar cell unit.
 2. The electronic watchaccording to claim 1, wherein said light transmitting material and saidreflecting plate are disposed adjacent to each other under the lighttransmitting digital display means to provide a high contrast at thelight transmitting digital display means, said solar cell being providedonly under the light transmitting material.
 3. The electronic watchaccording to claim 2, wherein said light transmitting material and saidreflecting material are disposed under about half of the lighttransmitting digital display means, respectively.
 4. The electronicwatch equipped solar cell according to claim 1, wherein the lighttransmitting digital display means is disposed so as to extend over theentire display window.
 5. The electronic watch according to claim 1,wherein the light transmitting material is formed of a translucentmaterial and the light transmitting material transmits light andreflects a part of the light to function as a reflecting plate for thelight transmitting digital display means.
 6. The electronic watchaccording to claim 1, wherein the light transmitting material is made ofa ceramic.
 7. The electronic watch according to claim 1, wherein thelight transmitting material transmits about 50% of the light andreflects the remainder which is about 50% of the light.
 8. Theelectronic watch according to claim 1, wherein the light transmittingdigital display means is provided with a hand type analog display means.